Calcium makes me think of chalk and orange juice. It's an essential nutrient: Your bones need calcium to grow and stay strong, and milk is a good source, hence the popularity of milk for children. So it might come as somewhat of a surprise to learn that calcium is a reactive alkali earth metal. It's not just a sort-of metal, it's an outright shiny, malleable, machinable metal. It has to be kept under oil or inert gas because it reacts with water (not violently like sodium, but fast enough that it won't last long in moist air). This still seems strange to me, even though I've seen (and hope to get soon) beautiful mirror-bright crystals of metallic calcium.

The explanation of course is that you never see elemental calcium in nature: It exists only as things like calcium carbonate (limestone) and the like.

Small lump 99.5%.
Kindly donated by David Franco, who sent many elements after seeing the slashdot discussion.Source:David FrancoContributor:David FrancoAcquired:17 May, 2002Price: DonatedSize: 0.1"Purity: 99.5%

10 grams under oil.
I'm hoping to get some really shiny crystalline calcium under argon soon, but this bottle has the advantage of being opened already, so if I want to do any experiments with the calcium, I can get to it without having to break a glass tube. Calcium is fairly reactive in air, so this bottle is filled with mineral oil, which has preserved a fairly clean surface on these metal chips.
When I hear the word "calcium" I, and probably a lot of people, think of a chalky powder, like a calcium supplement pill. But that's a salt, like calcium carbonate (which is, in fact, chalk). Pure calcium really is a metal, lustrous, malleable, the works.Source:eBay seller flabsterContributor:Theodore GrayAcquired:3 January, 2003Price: $10.50Size: 1"Purity: >99%

Sample from the RGB Set.
The Red Green and Blue company in England sells a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Hollow cathode lamp.
Lamps like this are available for a very wide range of elements: Click the Sample Group link below to get a list of all the elements I have lamps like this for. They are used as light sources for atomic absorption spectrometers, which detect the presence of elements by seeing whether a sample absorbs the very specific wavelengths of light associated with the electronic transitions of the given element. The lamp uses an electric arc to stimulate the element it contains to emit its characteristic wavelengths of light: The same electronic transitions are responsible for emission and absorption, so the wavelengths are the same.
In theory, each different lamp should produce a different color of light characteristic of its element. Unfortunately, the lamps all use neon as a carrier gas: You generally have to have such a carrier gas present to maintain the electric arc. Neon emits a number of very strong orange-red lines that overwhelm the color of the specific element. In a spectrometer this is no problem because you just use a prism or diffraction grating to separate the light into a spectrum, then block out the neon lines. But it does mean that they all look pretty much the same color to the naked eye.
I've listed the price of all the lamps as $20, but that's really just a rough average: I paid varying amounts at various eBay auctions for these lamps, which list for a lot more from an instrument supplier.
(Truth in photography: These lamps all look alike. I have just duplicated a photo of one of them to use for all of them, because they really do look exactly the same regardless of what element is inside. The ones listed are all ones I actually have in the collection.)Source:eBay seller heruurContributor:Theodore GrayAcquired:24 December, 2003Price: $20Size: 8"Purity: 99.9%Sample Group:Atomic Emission Lamps

Square block.
I still can't get over the fact that calcium is a metal, not a white chalky thing you eat to make your bones strong. This is a solid, squarish chunk of calcium metal, probably cut with some kind of sheers. Max and I got a couple of these to use in filming projects. It is stored under mineral oil, and I photographed it in the open air after just lightly drying it off with a paper towel. Calcium is relatively reactive, and will decompose on contact with water, but it's stable enough to stay shiny with just this minimal coating of oil.

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.

Hydrogen generator.
I got several of these little tin cans of calcium from an eBay seller who in turn got them, he says, from an auction at the Groton submarine base several years earlier. They are labeled with all sorts of military code numbers and warnings (which you can read in the rotation video, as they wrap around the whole can). I'm not clear on what they were meant to be used for, but it sounds like the idea was to drop the calcium chunks into water or perhaps an acid solution, at which point they will generate a steady stream of hydrogen gas until consumed. There are other chemical systems for generating hydrogen and I don't know why one would be preferred over another.Source:eBay seller pcijmaContributor:Theodore GrayAcquired:19 November, 2005Price: $13Size: 3"Purity: 99.9%

Autunite.
I bought some Fiestaware plates from Jim to use in museum displays I'm helping coordinate, and he threw in this little sample of Autunite, a uranium mineral. He probably has Fiestaware available if you need some.Source:Jim MarkitellContributor:Jim MarkitellAcquired:30 May, 2003Price: DonatedSize: 1.5"Composition:Ca(UO2)2(PO4)2.10H2O

Banded Fluorite.
The tag that came with sample reads as follows:

Banded Fluorite, Sierra County, New Mexico
This specimen was found in the steep section of tailings of an abandoned mine. Also included with some specimens are quartz, barite, granite and/or jasper. It fluoresces a nice vibrant purplish blue in both short & long wave ultra-violet light.

Fluorite Crystals, Kendall Mtn. near Silverton, San Juan County, Colorado.
This specimen was found in the steep section of tailings of an abandoned mine. These crystals fluoresce a nice vibrant powder blue or purplish blue in ultra-violet light.

Very large fluorite. (External Sample)
This is a huge, flat slab of fluorite crystals from the (now closed) mines in Southern Illinois. It is illuminated from the opposite side to show the translucence of the crystals.Location:John Gray's CollectionPhotographed:3 December, 2004Size: 24"Composition:CaF2

Fluorite.
This crystal is one I bought years ago but only recently found in a box. It's probably from southern Illinois but I don't really know, having long ago lost the tags.Source:Theodore GrayContributor:Theodore GrayAcquired:15 January, 2005Price: UnknownSize: 6"Composition:CaF2

Fluorite.
This crystal is one I bought years ago but only recently found in a box. It's probably from southern Illinois but I don't really know, having long ago lost the tags.Source:Theodore GrayContributor:Theodore GrayAcquired:15 January, 2005Price: UnknownSize: 5"Composition:CaF2

Autunite.
Autunite, if it is not kept in a humid environment, tends to degrade due to loss of water from the crystal matrix (see formula below, which indicates there are 10 molecules of water associated with each atom of uranium). This sample flaked apart as I was trying to mount it for photography, dropping little leaves of radioactivity everywhere. Still, quite pretty.Source:eBay seller dr**zarkoffContributor:Theodore GrayAcquired:10 June, 2005Price: $15Size: 0.5"Composition:Ca(UO2)2(PO4)2.10H2O

Autunite.
This autunite was donated by the mine owner who dug it up: It's a lovely specimen, photographed here under ultraviolet light. You can get samples of this an other radioactive minerals direct from the mine.Source:eBay seller boomologistContributor:Theodore GrayAcquired:25 June, 2005Price: DonatedSize: 1.5"Composition:Ca(UO2)2(PO4)2.10H2O

Autunite.
This autunite was donated by the mine owner who dug it up: It's a lovely specimen, photographed here under ultraviolet light. The main picture for this sample actually shows the back side of the sample, which has some very nice large crystals. The front side is completely covered with more autunite crystals: Click the turntable icon on the right to get an image you can rotate around and see from all sides.
You can get samples of this an other radioactive minerals direct from the mine.Source:eBay seller boomologistContributor:Theodore GrayAcquired:25 June, 2005Price: DonatedSize: 1.5"Composition:Ca(UO2)2(PO4)2.10H2O

Aeschynite.
The card that came with this shale-like blackish mineral says the following about the name: "From Gk. aeschyne, shame, alluding to the inability of chemists at the time of its discovery to separate some of its constituents". Hm, I wonder if it was the chemists who came up with this name, or the geologists who gave it to them to analyze.
This specimen is from Molland in Iveland, Norway. I bought it for its thorium content: Not that many minerals contain thorium and I'm trying to collect them all.

Reader Magnus Alvestad sent this interesting information about Iveland:

Hi. I noticed that your Aeschynite sample is from Iveland in Norway. The small community of Iveland is actually famous for their mines and minerals. Here's a folder with some information about a local exhibition. They also have at least 5 mines that are open to the public for a small price, where you can dig for minerals yourself.

The name "asbestos" used to mean a wonder-material, an insulator without equal and a strengthening fiber so cheap and strong it was used in building materials worldwide. Today the name means nothing but death and ruin.

Asbestos had been used so widely and for so long that it must have seemed beyond credibility when evidence first started appearing that it might be harmful. It is, after all, just a natural mineral, a rock dug from the ground. It contains no toxic elements or compounds. As a silicate mineral, asbestos is a member the group of minerals that make up as much as 90% of the earth's crust. How could such a common rock possibly be dangerous?

The answer lies in its shape. As you can see from this and the other asbestos samples below, the difference between asbestos and other silicate minerals is that asbestos appears in the form of very fine hair-like fibers. This fibrous nature is what makes it so useful as an insulator and building material: It can be woven, braided, pressed into mats, or mixed with plaster or concrete to make a strong, fiber-reinforced material. (It's also fireproof and impervious to most chemicals: What more could you ask for? To this day there are no really satisfactory substitutes for some applications from which asbestos has been banned.)

The fibers are not just fine, they are ultra-fine: The ends of the natural fibers taper down to molecular sharpness, with a tip that is literally no more than a few atoms across. Lodged in the body, most commonly in the lungs when stray fibers are inhaled, these tips can worm their way into individual living cells and tickle the DNA in a way that no blunt artificial fibers can.

The ability to touch, and damage, DNA makes asbestos fibers potent carcinogens: Remarkably, unlike virtually all other carcinogens, they cause cancer purely mechanically, not chemically or by radiation. They literally poke the strands of DNA in a living cell without killing the cell. Topping off their deadly potential, asbestos fibers, unlike for example modern fiberglass fibers, last pretty much forever in the environment of the lungs. Fiberglass is said to dissolve after a few months in the lungs, and in any case isn't sharp enough to cause molecular-level damage (at least, that's what people think now, we'll see how the evidence stacks up in another 50 years). But asbestos fibers will sit there for decades on end, firmly lodged in the deepest recesses of the lungs, just waiting for some unlucky DNA to happen by.

In principle asbestos could cause cancer anywhere in the body, but it's the lungs that are most vulnerable. As with many hazards, its layer of dead cells protects the skin from asbestos, as does the lining of the gut. But in the lungs the living cells are right on the surface, vulnerable to anything that finds its way past the nose and sinuses.

The most serious disease caused by asbestos is mesothelioma, a form of cancer. If you look up mesothelioma in google, you will find lawyers, lawyers, and more lawyers. Everywhere you look, it's lawyers as far as the eye can see. Even websites that seem to be purely informational or medical in nature will, on closer examination, turn out to be sponsored by a law firm. The reason of course is that there is big money in mesothelioma, specifically in suing any and every company that ever had its doorstep darkened by a product containing asbestos in any form.

There is probably some guilt in the asbestos industry. The real truth will most likely never be known, since to admit it would mean instant financial ruin for anyone who spoke, but my guess is that some people, including some senior people at large companies, knew pretty well that asbestos was harmful, and instead of immediately shutting their companies down and putting hundreds of people out of work, they tried to hide the evidence and thus condemned more workers and customers to death. (Business is complicated, much like life.)

But the current orgy of asbestos litigation is clearly targeting people far from any reasonable definition of guilt. Lawyer's websites list literally hundreds of companies and job sites, including small plumbing distributors, hospitals, schools, and even court houses. All places where asbestos was manufactured, sold, handled, or used. All places liable to being sued for millions of dollars by someone who wishes to hold them accountable for the disease that is slowly but surely killing them.

Saying that a small plumbing company that sold or installed asbestos insulation is liable for the illness of its workers or customers throws common notions of liability on their head. These small business people had no more reason to believe asbestos was dangerous than did their employees and customers: No one imagined it. No one considered it. No one would have believed it. And if some large companies had internal documents suggesting there was cause for concern, they certainly didn't share those with the local plumbing contractor!

A lot of good people have been ruined by asbestos litigation. But a lot of people have died because of asbestos, and juries tend to want to find a way to help sick people, even if it means extracting money from someone who did nothing wrong, someone whose only guilt is being in the wrong place at the wrong time. Which is to say, being the owner of a business that sold a legal product that they and everyone they knew thought was safe.

What would be a fair solution? Society benefitted from asbestos, society (which is to say the government) should pay to take care of those harmed by it. In most countries, that's just what happens (and not just for asbestos-related disease). But in America, we instead have a system in which we pick random companies and extort them for sometimes more money than they have, to enrich a few sick people beyond any reasonable need, while diverting a large percentage of the money to lawyers who, much as some people might wish it, don't even have mesothelioma. Those not lucky enough to find a target with deep pockets, or too honest to blame a blameless party for their misfortune, languish in poverty and pain until death takes them.

It makes about as much sense as throwing darts at a board to decide who pays for which disease: OK, Amtrack, you pay for lupus, General Motors gets colon cancer, Microsoft can take gastroenteritis, Chiquita gets mesothelioma, and for hives we will pick, oh, say, McDonald's. (Yes, Chiquita Bananas is on the list of companies targeted for asbestos litigation. The other company-disease associations I made up and have no basis in fact. So far as I know.)

One thing that is often missed in discussion of asbestos is that the minerals it comes from are beautiful! I bought a set of six absolutely stunning mineral samples representing the range of natural sources for this amazing product.

The photo associated with this text is of Actinolite, one of the most potently carcinogenic forms of asbestos. Its sharp, needle-like fibers make it especially dangerous. The samples below represent all the major natural sources of asbestos fibers.

Confiscated Davidite.
This mildly radioactive Davidite ore was confiscated from a student who brought it to school, not realizing that schools tend to freak out about radioactive things, whether they are truly dangerous or not. The original source is United Nuclear and it's perfectly legal.Source:AnonymousContributor:AnonymousAcquired:8 May, 2007Text Updated:9 May, 2007Price: DonatedSize: 1"Composition: (La,Ce,Ca)(Y,U)(Ti,Fe)20O38

More confiscated Davidite.
This mildly radioactive Davidite ore was confiscated from a student who brought it to school, not realizing that schools tend to freak out about radioactive things, whether they are truly dangerous or not. The original source is United Nuclear and it's perfectly legal.Source:AnonymousContributor:AnonymousAcquired:8 May, 2007Text Updated:9 May, 2007Price: DonatedSize: 1"Composition: (La,Ce,Ca)(Y,U)(Ti,Fe)20O38

Quicklime.
Quicklime is calcium oxide (CaO). It used to be employed to make light. Limelight. These days its main applications are in mortar (it turns into limestone on exposure to air and water), and in disposing of bodies.Source:eBay seller lauram300Contributor:Theodore GrayAcquired:8 May, 2007Text Updated:9 May, 2007Price: $36Size: 1"Composition:CaO

Soda-lime glass Medallion.
I made this medallion for an article in my Popular Science column, using a charcoal grill to melt the ingredients (silica sand, washing soda and limestone) together into soda-lime glass. Once melted I pressed the glass (darkened by ashes from the fire) into a graphite mold I had machined and heated in the fire.Source:Theodore GrayContributor:Theodore GrayAcquired:26 October, 2008Text Updated:26 October, 2008Price: $1Size: 2.5"Composition:SiO2+Na2CO3+CaCO3

Calcium hydride canister.
This canister is meant to be used to generate a volume of hydrogen gas to inflate a weather balloon. I think you poke out the indentation on the top and add water, but I'm not sure.Source: eBayContributor:Theodore GrayAcquired:28 February, 2009Text Updated:1 March, 2009Price: ForgotSize: 6"Composition:CaH2

Pretty seashell.
This pretty example of calcium carbonate was made by some kind of seashell making sea creature and washed up on a beach in Florida, I think.Source: FloridaContributor:Theodore GrayAcquired:28 February, 2009Text Updated:1 March, 2009Price: DonatedSize: 2"Composition:CaCO3

Coral.
Very beautiful and rare Hawaiian coral, traded for a poster and some nickel and copper nodules. This is the information that came with it:

Hawaiian Precious 'Pink Beauty' Coral

Precious coral has been for centuries prized by the people in Japan-third in value after gold and silver-because of its fine dense quality, its exquisite colors, and because it always has been associated with 'good luck,' and for several hundred years, expert craftsmen in several coral centers of Japan have been fashioning such precious coral of various shades and colors into fine pieces of jewelry-ornaments for Obi Clasps, kanzashi (ornamental hair pins), and more recently into rings, pendants, necklaces, and brooches This precious coral is completely different from black coral. Whereas black coral is merely an organic compound, precious coral is a calcium carbonate crystal commonly known as calcite, and is composed of hard skeletons of certain marine organism and grows very slowly, possibly at a rate of approximately one inch every 200 years, and in Hawaii occurs in colors from a salmon red, dark pink, pink, pale pink to snow white. 'Angel Skin' is the term commonly applied to the dark pink and medium pink shades.

The precious coral you have in your hand is a representation from only several hundred pounds of which were harvested from a depth of 1200 to 1500 feet (the length of 4 to 5 football fields) in the Molokai Channel, only a 'stones throw' from the Makapuu Lighthouse on the island of Oahu and is therefore genuinely Hawwaiin. The 'ground' which was discovered by University of Hawaii scientists in the fall of 1966 is so far the only known production area in the island chain, and several attempts to locate other grounds in the waters of the Hawaiian Islands have been unsuccessful. Precious Coral-the prefect gift and souvenir of Hawaii-from Hawaii-buff it, polish it, fashion it into jewelry of your own design, or just save it as a memento of your prefect Hawaii vacation.

Colored Chalk.
Simple writing chalk, which is made of gypsum, not the rock also known as chalk.Source: Hobby LobbyContributor:Theodore GrayAcquired:2 April, 2009Text Updated:3 April, 2009Price: $2Size: 4"Composition:CaSO4

Quicklime Desiccant.
This interesting little desiccant packet came in something I got from China. Most desiccant packets (which are packed up with many products to keep them dry during shipping) are made with silica gel, but this one is made with quicklime (calcium oxide, CaO). The difference is that if you pour water on silica gel it doesn't do much of anything, but if you pour water on quicklime, it becomes so hot it boils the water, producing steam and spitting hot water out.Source:Theodore GrayContributor:Theodore GrayAcquired:12 January, 2010Text Updated:12 January, 2010Price: DonatedSize: 3"Composition:CaO

High purity crystals. (External Sample)
These are industrially produced high-purity calcium crystals of the highest grade. They are shiny, soft enough to tear apart by hand, and sealed in a glass ampule because they would react with air and tarnish within seconds. Unfortunately I cannot reveal their location as the company that makes and uses them in their work is very sensitive about trade secrets: I had them on loan for a few weeks to photograph for a film project, then sadly they were destined to be turned into something quite a bit less beautiful.Location:AnonymousPhotographed:10 April, 2005Size: 1"Purity: >99.9%